Well screen



May 28, 1946. s. M. AKEYON ETAL WELL SCREEN 'Filed Jan. 26, 1944 MAKEYsO/v SWAN e0 42 STOCK/{AM INKENTOR.

Patented May 28,' 1946 "2,401,035 t t y v WELL SCREEN.

Swan M. Ak eyson ,and'Ward L s tockham, Long r Beach,- Calif., assignors to Nobs Chemical Compa ny, Los Angeles, Calif.,- a corporation of Cali- ApplicationJanuary 26, 194 4,"Serial:No;519;740

, n V 7Claims. (Cl. 1 6 6 v n A This invention has to do with the conditioning T The invention provides for the use o'fascreen of well screen, by which term we include gener- -aperture filling material having various properally various types and forms of apertured or perties and prerequisites giying it' outstanding-sultforated pipe sections or linersthrough which proability for this purpose, "In meeting the requireduction fluid is taken from the "formation into 5 ments of such amaterial, one main purpose ofthe ground surface.

the well casing or flow pipe for delivery to the invention is to provide an aperture filling composition which is substantially insoluble in crun- In il well'drilling and producing operations affected by the normal wellfluids, i. e. oil and.

the casing may be run through one or more oil water, but which is actively attackable by acid,

producing strata, from which it may not be de- 10 say a solution of hydrochloric acid, toa degree sired to take production until some later orinpermitting ready. disintegration of the material definite future time. Accordingly, one of the and resultant opening of the apertures; Thus most general practices has been to lower standwith its apertures initially filled by the material,

. ard casing through I intermediate oil bearing a the screen is capable ofrem'ainingin closed constrata and to cement off the oil sands at theoutdition within the well despite immersion in the side oflthe casing for. future production. Then" well fluids, andyetis capable of becomingfully when itis'desired to take productionfrom an inopened by the acid treatmentpsay at .s'uchtime termediate sand, the section of the casing oppoas it is desired totake production through: the site the sand has been perforated by cutting or screen. i

; punching tools, or by gun-type perforators, low- The invention contemplates usingan aperture ered in thewell. Another'method'has been to filling material which is predominantly composed "inltallyfill the apertures of standard perforated of one or" a mixtureof the substantially water .pipe'or liner with a solid substance, such as sulinsoluble metallic carbonates. The general class .phur, which lateris dislodged by creating an 'exincludes the carbonates-of calcium, magnesium,

plosive force within the pipe. The apparent disbarium, strontium and zinc. Among these, ceradvantages of this method are the disruptive tain carbonates are -.especially advantageous by strains imposed on thepipe orscreen, and the reason of their susceptibility to the desired acimpossibility of assuring removal of the filling ,tion and effect ofthe acid treatment, and for materialfrom allthe apertures.

forming with additional components oi the mix- Our primary object; is toprovide improved 0 ture, a hardened'homogeneous masseffectively' screen-filling materials and method of using resistantto accidental dislodgementflfrom:the

- same, whereby it ispossible to retain all the adapertures. .Calcium carbonate is used as apree vantages of a preformed screen having a predeferred component of the material byreasonof terminecl and most eflicient aperture size and arits ready attackabllty by the acid solution and the rangement,.and also a normally closed structure resultant disintegrationand removalofthe mathat may be'opened atany time after placement, terial fromtthe apertures. It is. found thatthe in the well toclearthe apertures for inflow of material maybe given superior properties" with production oil; all in a manner assuring comrespect to its hardness and permanency or sta-.

.with the broadaspects of the invention, wemay' bonate.

plete clearing ofrthe-apertures and without inbilityias ahardened mass, by the use of magjury to' the screening medium. In accordance 0 nesium carbonate together with the calcium caruse well screen of various known types in which The magnesium carbonate used preferably is the'aper-tures may be formed in any'suitable mana calcined or partially dehydrated magnesite ner, size and arrangement. In order that the whichby reason of its preecalcination, iscapa screen'normally; i. e. when first placed in the bleof hydration or acquiring-water of combinawell, will have, a closed-structure preventing fluid .tion, and is further capable when mixed with the flow-into whom the screen section of the cascalcium carbonate and magnesium chloride soluing, the screen apertures are closed by a material tion, of causing the mixture to set and form a capable of later being removed by an acid reagent hard mass. The calciumcarbonate and magne- "lr solventintroduced to the well. slum carbonate may be used in any suitable proused so long as portions,-.ranging for example in the case of each, from 20 to 70%. by. weight of v the mixture. Particularly satisfactory results have been 'obtained using betweenabout 40 to 45% each ofthe two carbonates. The latter desirably are finely ground, say in the order of 200-mesh or finer.

A suitable binder or' adhesive'is admixed with the carbonates; In the broad aspects of the invention, any-suitable adhesive or binder may be it isadequately resistent to dissolution-or attack by the well fiuids. Accordlngly, a suitable adhesive or binder maybe selected from the non-water soluble glues, and particularly those less affected. by hydrocarbons. The invention particularly contemplates, however, the-.selectionand use of -a binder not only for its adhesive qualities, but also its expansibility and capacity therefore for caus- .apertured well because of ing the mixture during the setting or hardening period, to expand within the screen apertures thereby forming ahlghly effective seal by reason both of theadhesive and the expanded condition of the mass. secure these advantages, casein preferably is used as the binder because of its low solubility'characteristics, adhesiveness and property of expanding after mixing with'water and being permitted to solidify. The casein content of. the mixture may be from'abo fi 2 to 10%.

The mixture ini ally is formed as a plastic mass for placement in the,.apertures by --mixing with the 'calcium' andmagnesium carbonates and casein, a-water solution of magnesium chloride at a concentraton of around '7 to 8 pounds of the salt per gallon .of.water.. The effect of themagnesium' chloride is to cause the magqualities of, the binder nesite to set and bind-the carbonates in a hardened and cement-like mass.

In addition to providing in the mlXture a high percentage of chemically 'disintegrable compo nents,=--the presence r: lboth calcium carbonate and magnesium carbonate is of great importance from the standpoint of giving the hardenedmixture' the essentialjdensity and high strength.

Upon hardening in the presence of the magnesi-- um chloride solution, the calcium carbonate and -magnesium carbonate form their binary or doublesalts, the stereo chemical structure of which that of either carbonate is quite different from above. It appears that the double salt is formed by the activation of thecrystalline surfaces of the two carbonates by the magnesium chloride, and itis possible that a surface solubilizing action takes place followed by sulting, uponicooling-in the formation of double salts having structural and chemical characteristics of single compounds; l a

For purposes of the present invention, the

a super-saturation reinside, the screen may aeoross the accompanying drawing showing a typical form'of well screen, it being understood, as indicated above, however, that the invention is independent of any particular type or form of scre'en'and is generally applicable to the conditioning of all such screens capable of being filled with a disintegratable material of the character described. In the drawing:

Fig. 1 is a sectional view of the normally open screen;

Fig. 2 is a. fragmentary longitudinal section showing the filling material in the screen aperture',

Fig. 3 is a section on line 3--3 of Fig. 2;

Fig. 4 is a view illustrating a method of filling the apertures with the material; and

Fig. 5 illustrates a variational embodiment of the invention in a gravel pack liner assembly.

Referring first to Fig. l, the screen may consist of a length of perforated well pipe or liner l0 having suitably formed apertures such as slots In applying the aperture filling material, a

plastic mixture thereof may be placed on a suitable fioor Or surface, as indicated at 12 in Fig. 4. After having inserted a temporary liner IS with-- in the screen to close the apertures II at the be rolled over the material I2 to cause the material to enter and become tightly compacted within the apertures. Thereafter, excess material maybe removed from the outside surface of the screen and the liner l3 withdrawn. The apertures ll thus are filled with acid soluble plugs 14 which as the material is allowed to set, become hard and tightly bonded to the'pipe by reason of the expansion and adhesive properties of thematerial.

Thereafter,- the screen may be lowered and.

set atiirhatever location desired within the well, and the screen may remain so placed and in its closed condition until such timeas it'is desired to open the apertures. A cid, for example an aqueous solution of hydrochloric acid, then may be introduced to the-inside of the liner by any suitable means permitting the. acid to attack and disintegrate the plugs 14 to open the screen for the in-fiow of fluid.

Fig.5 illustrates a further embodiment of the invention as applied to gravel pack liners, particularly of the pre-packed type. In their general form and construction, suchgravel pack liner assemblies comprise .an inner perforated pipe or liner l5, and an outer screen or perforatedpipe l6 annularly spaced from the inner pipe and suitably. attached thereto as by conpractical result and advantage is, as indicated,

that the double salt has the desired acid'solubility, while exceedingby virtue ofits crystalline structure, in the hardened mass, the strength obtainable by using either carbonate. The added effects of the organic pipe andin tending constantly to expand the material within the pipe apertures, thus complete all the properties required in the material to assure'its intended purposes, i. e. normally to form a hard, strong I curely bonded against displacement out of the aperture, and onenevertheless capable of effective disintegration and removal by acid treatment.

The invention, .including atypical method for placing .the filling material in the screen apertures, may be further explained by reference to 75 manner binder in adhering to the metal and wear-resistant plug senection l1 atthe upper and lower ends of the outer screen IE (only the lower end connection beingshown). Theannular space between the screens i5 and .16 is filled with a body of gravel l8 or other divided material forming in the assembly a foraminous bed. and third screening medium.

In accordance with the invention, it is made possible initially to close the inner and outer screens l5 and 16 against the passage of fluid into or through the screen and gravel assembly, and to protect the screen apertures against clogging by foreign materials during lowering and setting of the assembly in the well. Apertures l9 andZO of the screen sections l5 and I6 first are filled with the acid-soluble material in the previously described with reference to having apertures the liner l0, and the gravel I8 is filled into the space between the screens. At any time after the assembly has been set in the well, hydrochloric acid solution may be introduced to the interior of the liner i to first dissolve or disinf tegraie the aperture plugs 19, and then to flow out through the gravel to attack and disintegrate the plugs 20 in the outer screen.

passing medium, and a solid substantially oil and, water insoluble material closing the apertures of said medium, said material being composed predominately of finely divided particles of metallic carbonate held together by a substantially water insoluble adhesive tending in the and a binding substance tending in the presence of water to expand saidmaterial within the apertures. i 4. A well screen comprising an apertured fluid passing medium, and a solid substantially oil and water insoluble material closing the apertures of presence of water to expand said material within the apertures, and said material being readily attackable by hydrochloric acid solution to disintegrate the material and open the screen apertures.

3. A well screen comprising an apertured fluid passing medium, and a solid substantially oil and water insoluble material closing the apertures of said medium, said material containing particles of calcium carbonate and magnesium carbonate uniformly distributed in the material and in suflicient quantity to render the material readily disintegrable by hydrochloric acid solution said medium, said material comprising a hardened mass of metallic carbonate and casein as a binder, said material being readily attackable by acid to disintegrate the material to open the screen apertures.

5. A well screen comprising an apertured fluid passing medium, and a solid substantially oil and water insoluble material closing the apertures of said medium, said material comprising a hardened mixture of calcium carbonate, magnesium carbonate and casein, and the material being readily attackable by acid to disintegrate the material to open the screen apertures.

6. A well screen comprising an apertured fluid passing ,medium, and asolid substantially oil and water insoluble material closing the apertures of said medium, said material comprising, in parts by weight 20 to 70% calcium carbonate, 20 to 70% magnesium carbonate, and 2 t 40% casein, and the material being readily disintegrable by acid. I

7. A well screen comprising an apertured fluid passing medium, and a, solid substantially oil and water insoluble material closing the apertures of said medium, said material being formed by admixing finely divided calcium carbonate, magnesium carbonate capable of acquiring water of hydration, casein and magnesium chloride solution. SWAN M. AKEYSGN.

WiARD L. STOCKHAM. 

